+ # Write the full line for the element `e` in `o`.
+ #
+ # Basically it does:
+ #
+ # ~~~nitish
+ # o.write "{prefix}{display(e)}\n"
+ # ~~~
+ #
+ # Usually, you should redefine `display` to change the display of an element.
+ protected fun write_line(o: Writer, e: E, prefix: String)
+ do
+ o.write "{prefix}{display(e)}\n"
+ end
+